Legia Warsaw said on Thursday they feared being excluded from the Champions League after their fans clashed with the police before Tuesday’s League match at Real Madrid in a second incident of this kind in this season.

The Polish champions were hammered 5-1 after some of their fans were involved in violent clashes with police outside the stadium.

Twelve people were injured in the clashes, including three Spanish policemen, and 13 Polish fans were detained, according to Madrid government delegate Concepcion Dancausa.

Legia has already been fined by the UEFA for crowd trouble during their home game against Borussia Dortmund in September and will host Real Madrid in an empty stadium when they meet in the return fixture on Nov. 2.

That will be the fourth time they have had to play behind closed doors in Europe following three punishments in the Europa league since 2013.

“There have been unofficial suggestions before the Real Madrid game that any offence could result in excluding us from European competitions,” said Seweryn Dmowski, Legia’s public and media relations director.

“We did not receive any official letter from the UEFA but behaviour of their delegates suggests it is possible.”

UEFA could not immediately be reached for comment.

Legia are the first Polish team to play in the Champions League in 20 years but their campaign has been marred by poor results and crowd trouble during two of three games they played in Europe this season.